Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder that is incurable, progressive, manifested by muscle weakness and wasting, and caused by degeneration of motor neurones. The limited data available suggest the incidence of ALS in Canada to be approximately 2 per 100,000 persons. The disease is characterized by progressive weakness of respiratory muscles, leading to respiratory insufficiency which is often the cause of death in patients with ALS.